1. Technical Field
The present invention relates to a double balance electrical noise reduction device, RJ45 modular insert, and printed circuit board. The device is used for high frequency transfer of data signals to interface connectors for unshielded twisted pair media (“UTP”), and, more particularly, utilizes a low reactance modular insert with two stage positive and negative compensation techniques to produce low noise characteristics.
2. Background of the Disclosure
The wide acceptance of UTP for data and voice transmission is due to the large installed base, low cost, and ease of installation. Demands on networks using UTP systems such as 100 Mbit/s and 1000 Mbit/s transmission rates have increased, which has forced the development of industry standards requiring higher system bandwidth performance and lower noise-connecting hardware. What began as the need for connecting hardware to provide near-end cross-talk (“NEXT”) loss of less than −36 dB at 16 MHz, has evolved to −54 dB at 100 MHz and −46 dB at 250 MHz for future category 6 systems. As the transmission rates have increased, so has system noise, in particular NEXT.
For any data transmission event, a received signal will consist of a transmission signal modified by various distortions. The distortions are added by the transmission system, along with additional unwanted signals that are inserted somewhere between transmission and reception. The unwanted signals are referred to as noise. Noise is the major limiting factor in the performance of today's communication systems. Problems that arise from noise include data errors, system malfunctions, and loss of the desired signals.
Generally, cross-talk noise occurs when a signal from one source is coupled to another line. Cross-talk noise could also be classified as electromagnetic interference (“EMI”). EMI occurs through the radiation of electromagnetic energy. Electromagnetic energy waves can be derived by Maxwell's wave equations. These equations are basically defined using two components: electric and magnetic fields. In unbounded free space a sinusoidal disturbance propagates as a transverse electromagnetic wave. This means that the electric field vectors are perpendicular to the magnetic field vectors that lie in a plane perpendicular to the direction of the wave. NEXT noise is the effect of near-field capacitive (electrostatic) and inductive (magnetic) coupling between source and victim electrical transmissions. NEXT increases the additive noise at the receiver and therefore degrades the signal-to-noise ratio (“SNR”).
Cross-talk using a plug setup such as that illustrated in FIG. 1 will increase as the system speeds or system transmission frequencies increase. The transposition, or twisting of the transmitting wire pair, minimizes cross-talk generated in a cable. However, coupling occurs as the signal travels through untwisted sections such as plugs and plug contacts.
In a differential balance two wire per pair transmission system, the signals that travel along each wire (or other media) are equal in amplitude but opposite in phase. The phase difference of the two signals is ±n radians or voltage +1(E1)=−voltage −1(E2) under ideal conditions. These signals at any instantaneous time couple electric and/or magnetic fields to adjacent lines, which reduces their SNR. The acceptable SNR depends on the type or quality of service that is required by the system. To remove the noise components, a forward signal equal but opposite to the original signal is induced. According to Fourier's wave theory and Maxwell's theory of electromagnetic fields, by coupling the opposite phase of the transmitted signal to a previously coupled adjacent line signal, the two signals cancel each other completely and therefore remove the noise from the adjacent line.
The ANSI/TIA/EIA 568A standard defines electrical performance for systems that utilize the 1-100 MHz frequency bandwidth range. Some data systems that utilize the 1-100 MHz frequency bandwidth range are IEEE Token Ring, Ethernet 10Base-T, and 100Base-T. The ANSI/TIA/EIA will soon finalize a standard defining electrical performance for systems that utilize the 1-250 MHz frequency bandwidth range for category 6 electrical performance. The increasing demand for more bandwidth and improved communication systems (e.g. Ethernet 1000Base-T) on UTP cabling will require improved connecting hardware.
The TIA/EIA category 6 draft-addendum for channel link defines the specified frequency bandwidth of 1-250 MHz, and a minimum NEXT value of −39.9 dB at 100 MHz and −33.1 dB at 250 MHz.
By increasing the bandwidth from 1-100 MHz (category 5) to 1-250 MHz (category 6), tighter controls of component noise susceptibility is necessary. With the development of the new standards, the new connecting hardware noise levels will have to be lower than the old connecting hardware that were used in category 5 media systems.
Methods for providing positive compensation to reduce cross-talk noise in connecting hardware is addressed in U.S. Pat. No. 5,618,185 to Aekins and U.S. Pat. No. 5,299,956 to Brownell et al., the contents of which are hereby incorporated by reference.
FCC part 68.500 provides standard mechanical dimensions to ensure compatibility and matability between modular plug housings of different manufacturers. Two basic modular plug housing types are produced based on the FCC part 68.500 standard. Type one is the standard FCC part 68.500 style for modular plug housings which does not add any compensation methods to reduce cross-talk noises. Type two is the standard FCC part 68.500 style for modular plug housings which add compensation methods to reduce cross-talk noises.
The type one modular plug housing provides a straightforward approach by aligning connector contacts in an uniformed parallel pattern where high NEX and far-end cross-talk (“FEXT” is produced. The standard FCC part 68.500 modular plug housing connectors defines two contact sections: a) section one is the matable area for electrical plug contact; and b) section two is the output area of the modular plug housing. Section one aligns the contacts in an uniformed parallel pattern from contact tip to the bend location that enters section two. Forming a contact in such a manner will produce high NEXT and FEXT noises. Section two also aligns the contacts in an uniform parallel pattern from contact bend location to contact output, thus producing and allowing high NEXT and FEXT noises.
There have been attempts to reduce cross-talk noises in electrical connectors. For example, U.S. Pat. No. 5,674,093 to Vaden discloses a reduced cross-talk electrical connector including a housing that receives four pairs of elongated contacts for receiving electrical signals. One contact of each pair of contacts is irregularly bent into an “S” shape in order to reduce the parallelism between adjacent contacts. By reducing the parallelism between adjacent contacts, coupling effects between the contacts is reduced. Although crosstalk noise is reduced, the circuits return-loss and differential impedance is increased for all four pairs. In addition, it is difficult to form such irregularly shaped contacts.
The type two modular plug housing is the standard FCC part 68.500 style which add compensation methods to reduce cross-talk noises. An example of such a modular plug housing is disclosed in U.S. Pat. No. 5,639,266 to Patel. U.S. Pat. No. 5,639,266 provides a compensation approach for modular plug housings by aligning the contacts of the opposite pairs in an uniformed parallel pattern to removed cross-talk noises. The connector disclosed in U.S. Pat. No. 5,639,266 is defined by two contact section areas, section one is the matable area for electrical plug contact and section two is the output area of the modular plug housing. Section one aligns two contact positions, i.e., positions 3 and 5 out of 8, in an uniformed parallel pattern from contact tip to the bend location that enters section two, thus reducing cross-talk noises by signal compensation. Section two also aligns the contacts in an uniformed parallel pattern from contact bend location to contact stagger array output, which minimizes NEXT and FEXT noises.
From the above it is apparent that what is needed is an improved UTP connector that reduces connecting hardware cross-over talk NEXT noise. Importantly, the improved connector should not lessen the impedance characteristics of connected wire pairs. Furthermore, the improved connector should satisfy the new modular plug housing noise levels as provided in the new category 6 standard.